1. Field of the Invention
The present invention relates to technology for providing high reliability for a system using plural logical computers running on an identical physical processor.
2. Description of the Prior Art
The advance of processor technology has enabled high-performance processors to be easily used. Conventionally, insufficient performance has been covered by running plural logical computers in parallel. With the advent of high-performance processors, however, performance has been satisfied and concerns are shifting to how to effectively use the high-performance processors. A logical computer function is one approach to the effective use of the high-performance processors. The logical computer function is technology for creating plural virtual computers from one physical computer. For example, if one physical processor is assigned to plural logical computers in a timesharing mode, it could appear to software that plural computers exist. This function allows effective use of one high-performance processor. There is an example that further develops the logical computer function to provide higher reliability. In US005345590A, a description is made of a method which builds a hot standby with two logical computers, and when one of them fails, switches to another logical computer to continue processing. The hot standby method is a method for achieving high reliability usually with different computers. According to this technology, two different computers are provided so that processing is normally performed by one computer, and if a failure occurs, switching is made to another standby computer without stopping processing. In US005345590A, a hot standby is built between two logical computers created on an identical physical computer. This contributes to an increase in reliability of system level.
In the US005345590A, a description is made of a method which increases reliability by building a hot standby with two logical computers. Although this method describes a method for increasing the reliability of software level, a reliability method combined with hardware is not described. A problem with the US005345590A is that, when one physical processor is disabled due to a hardware failure, plural logical computers configured on the physical processor to build a hot standby fail at the same time, making the hot standby useless. For example, if two logical computers are created on one physical processor to build a hot standby, a failure of the physical processor would cause the logical computers built on the physical processor to be stopped.